Does this setup seem sufficient?
After reading many of the articles and comments here, I’ve been inspired to try and build Passive House insulation and air tightness.
I’ll share what I’m thinking so far with the hope that maybe you can direct me in any way. Not necessarily trying to get Passive House certified, but would like to build airtight anyway.
Region: west mountains of Dunlap, TN
Slab:
at or on grade: gravel, moisture barrier, 2″ or 3″ of EPS (only companies I know PermaR and ThermalStar), maybe 6″ to 12″ of sand (for thermal mass, inspired by the following link at 45:00 minutes: https://www.youtube.com/watch?v=AtHkvpRI6fc), wire mesh or re-bar, radiant floor heating pex, and poured concrete slab.
Some people say put the poly moisture film over the sand and EPS boards but I don’t think that’s correct ???
Walls:
2×4 16″ o.c. with sill seal and accoustic sealant under sole plate. Roxul R-15 rockwool/Mineral wool insulation in between studs with the ZIP (about $14 for a 4’x8′, but I don’t like that it’s OSB since plywood is much stronger) for sheathing and maybe Tyvek (sealed with tape as a secondary air barrier; belt and suspenders approach)
with either 2.5″ of EPS on top (R-10 from InSoFast) OR UX2.0 (R8.5) and the EX2.5 (R10) for a
total of 4.5″ of EPS (R18.5)
Also, maybe instead of the ZIP sheathing, using plywood with the Prosoco sealants. https://www.prosoco.com/product-use?term=Exterior%20Sheathing
OR using plywood with StoGuard sealant and Gold Coat
http://www.stocorp.com/air-moisture-barriers/
Attic ceiling: I’ve been thinking of sealing it off with ZIP (OSB) or plywood and ZIP tape (or StoGuard), putting Roxul R-15 rockwool/Mineral wool insulation between the truss bottom chord and then putting R-38 fiberglass batts on top of the plywood. I need an open attic so maybe an open energy truss (if that exists) but I don’t know if my design will allow for that. I have a large open center space that I don’t know how expensive it would be to get a beam that long. I’ll attach a floorplan.
Roof: I thought of just leaving it alone, maybe just adding a radiant barrier by atticfoil.com. Metal standing seam roof.
Heating and Hot Domestic water: wood cook stove (maybe a wood boiler so that I don’t have to fire the stove), solar water heater, and a Vaughn 119 gallon solar tank (http://www.vaughncorp.com/products/solar/#proddoc) all hooked up using natural thermosiphon. Radiant Floor Heating (will require an ECM pump).
Cooling: maybe an LG or Mitsubishi split ductless unit.
Windows: I don’t know, but I’m waiting to see what Klearwall quotes me on some Casement windows (planning on installing them.”innie” style.
Power: off-grid an 8kW Magnum system
Water: a well, currently looking for an ECM model
Ventilation: I’ve been considering and ERV by Zehnder or UltimateAir 200DX or a RenewAire EV90P
Price is the limiting factor, but maybe if I with a contractor friend of mine do the bulk of the work, maybe it will work. Interior of the house will be gypsum boards and wood and tile floors. Also, once I get the outside done maybe I can progress as funds are available.
Any help would be greatly appreciated,
Edwin
P.S. Does anyone know if this statements are true?
“ordinary polyethylene films can deteriorate in a relatively short time, even when sealed within a wall or buried under a concrete floor. “
“Tenoarm is resistant both to oxidation, the principal cause of polyethylene failure in walls, and to alkali attack, the principal cause of polyethylene failure under concrete slabs” http://conservationtechnology.com/building_films.html
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Replies
If you're going to build to PassiveHouse standards the PHIUS design tools would be able to tell you what works or doesn't.
http://www.phius.org/software-and-technical-resources
If you're going for something like Net Zero Energy (a more affordable goal) see Table 2 p.10 of this document:
http://buildingscience.com/file/5806/download?token=GouEIX9Y
Note, those are "whole assembly R" values, with all thermal bridging factored in.
Depending on your exact location you're either on the warm edge of zone 4 or the cool edge of zone 3. An example of an R20-R25 whole-wall assembly (zone 3 recommendation) would be 2x6 /R23 rock wool with 1.5" ZIP-R
If you're going to be off grid you'll get more heating efficiency out of an oil fired wall furnace than a diesel fired generator + mini-split. A better solution would be to use a small wood stove for heating, and the lowest input power mini-split size to be able to run during daylight hours with roof mounted PV, or just design the cooling load out of it and use a nighttime ventilation strategy (to the extent possible.)
At the cost of diesel fuel you get pretty good paypack on PV, which is why even coal mining operations worldwide are installing PV at remote mine sites to run the bulk of the power for the operations.
Polyethylene deteriorates under direct UV light, but if you have UV light under you slab you have more serious problems than deteriorating PV! :-) Don't sweat that one too much- I've seen 40-50 year old 6 mil polyethylene pulled from walls that was still flexible & functional. If your nature is to worry, use EPDM (membrane roofing material.)
Radiant barrier is pretty useless stuff in an insulated attic with no ducts. Design the attic an truss chord loading to be able to handle ~18" of cellulose to hit the R50-R60 levels indicated for zone 3-4 in the BSC document, and you won't have to worry about the roof gains.
Unrelated but will UV damage wood?
Given the existence proofs of 1000 year old unpainted stave buildings in Norway, wood can take the UV long enough for most purposes.
http://2.bp.blogspot.com/-5EsZjYL7WyU/UzWavEEVFiI/AAAAAAAAM98/0y8OkVtKkMg/s1600/IMG_7237.JPG
cool, the building is presumably older then the tree it came from lived
Edwin,
Your details need to be adjusted somewhat.
You don't want sand on top of the polyethylene under your slab. That's a big no-no. For more information on this issue, see Polyethylene Under Concrete Slabs.
I've lived off-grid for 40 years, and I don't recommend that any off-grid house include air conditioning. The limiting factor is the size of the necessary batteries, which get very expensive very fast. In general, off-grid homes are heated with either a wood stove or a propane-fired space heater with through-the-wall venting, and are cooled with ceiling fans or (in dry climates) a swamp cooler.
I also don't recommend installing an HRV or an ERV if you live off-grid. It takes a lot of electricity to run this type of mechanical ventilation system, and you won't have much electricity during the winter.
Maybe it's just me, but I wasn't able to follow your description of your ceiling insulation plan. What is an "attic ceiling"? Does that mean your roof sheathing? Or maybe a sloped ceiling that follows your rafters (under the rafters)? Or is it what many people call an attic floor?
Dana: I’ll consider myself zone 4, since up on the mountain it’s about 4° cooler than in the valley.
Heating Winter: wood stove to cook, heat home and heat domestic water (passive -thermal siphon).
Supplemental Heating Winter: I’ll use the wood stove to heat domestic water by using a water Jacket or two if necessary, I’ll use the water for radiant heating. If system does not produce enough hot water then I’ll upgrade to a gasification wood boiler and use the wood stove sparingly.
Heating summer: an electric stove to cook and a solar thermal panel to heat domestic water (passive -thermal siphon).
Supplemental Heating Summer: PV array with the water tank’s electric heater.
Cooling: mini-split
For my wall assembly I was looking at: drywall R0.45, 2x4 Rock wool R15, OSB R0.51, and 2.5” EPS R10 on the outside = R25.96 (will look at price to add 2” of Roxul R8 on top of the EPS)
Ceiling: drywall R0.45, between ceiling joist Rock wool R15, plywood R0.62 sheathing on attic side of ceiling joist (every joint sealed) with R38 Fiberglass insulation on top (vented attic) = R54 (need 6 more for R60)
Sealing products: ZIP system sheathing and roof, and/or StoGuard Emerald Coat, and/or Prosoco Cat 5
Slab: EPS ThermalStar X-Grade 2” R8.4 (everywhere) and a 4”-5” slab on grade. (will look at price to add 2” R8 -3” R12 of Roxul under EPS)
Electricity: A 48V 1576Ah battery setup. A Magnum 7.56kW PV Array (top-of-pole-mount) that I can “easily” build up to 11.34kW if necessary.
Martin: Thanks for the article it gave me a lot of answers I’ve been looking for. I skip the sand, although I don’t know about putting the EPS under the Poly because I’m in a heave to very heavy region for termites (especially in the woods).
I think I’ll have enough power for an ERV in the summer and if I don’t for the winter then I’ll just put more logs in the fire and crack the windows. (This will also help produce more hot water which will make for good radiant heating.)